"FLiRT" COVID variants are spreading. Scientists share what we know so far.

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More than a 3rd of COVID-19 cases successful the U.S. are present estimated to beryllium from a new, fast-growing subordinate of a radical of alleged "FLiRT" variants, nicknamed for their tiny but distinctive changes comparative to the JN.1 strain. JN.1 was the variant down this past winter wave of infections.

The largest among them, called KP.2 by scientists, has rapidly multiplied successful caller weeks to go the now-dominant caller COVID-19 strain. 

According to the Centers for Disease Control and Prevention's every-other-week variant estimates, KP.2 and different strain with the aforesaid FLiRT mutations, called KP.1.1, unneurotic marque up a projected 35.3% of infections this week. This is up from 7.1% a period ago.

"That means that portion KP.2 is proportionally the astir predominant variant, it is not causing an summation successful infections arsenic transmission of SARS-CoV-2 is low," a CDC spokesperson told CBS News successful a statement.

The strain besides does not person ample amounts of worrying changes, dissimilar immoderate antecedently highly-mutated variants that person raised alarm successful years past. 

However, the swift alteration successful circulating variants has resulted successful the Food and Drug Administration this week delaying a cardinal measurement successful its process for picking retired the strain to people with this fall's COVID-19 vaccines, citing the request for much "up-to-date" data.

While national requirements for hospitals to study COVID-19 information to authorities lapsed this month, the CDC says it inactive has reliable figures from sources similar wastewater investigating and exigency rooms to proceed tracking activity from the virus. 

Here's the latest of what we cognize astir COVID-19 variants successful the U.S.

What is the existent caller variant of COVID-19?

According to the latest projections published by the CDC, astir 28.2% of COVID-19 cases nationwide are present being caused by a sublineage of the microorganism called the KP.2 variant. 

The adjacent largest variant connected the emergence is different JN.1 descendant called JN.1.16. That strain has not grown arsenic quickly, lone inching up to an estimated 10% of cases this week.

That projection is based connected familial sequences of the microorganism reported by mostly nationalist wellness labs, which person dropped importantly successful caller weeks alongside the slowdown successful cases overall. Other CDC information from wastewater and traveler investigating inactive does not abstracted retired KP.2 from its JN.1 parent.

KP.2 is simply a intimately related descendant of the JN.1 variant from this past winter, which turned retired not to beryllium importantly much severe than the variants that were ascendant earlier it, contempt its ample fig of mutations.

"So it's 1 that we are watching. It's 1 that we are monitoring. And again, reiterate the request for continued surveillance of SARS-CoV-2 successful radical astir the world, truthful that we tin show this evolution," the World Health Organization's Maria Van Kerkhove told reporters Wednesday.

Why are these COVID-19 variants called FLiRT?

The nickname FLiRT comes from 2 distinctive mutations seen successful respective descendants of the JN.1 variant that person sprung up astir the satellite aft its expanse implicit the winter. Some of the largest strains with FLiRT mutations successful the U.S. close present are KP.2 and KP.1.1.

"It is fundamentally conscionable making a connection retired of the circumstantial amino acerb changes successful the spike macromolecule F456L + R346T, oregon phenylalanine (F) to leucine (L) astatine presumption 456 and arginine [R] to threonine [T] astatine presumption 346," Canadian biologist Ryan Gregory, a prof astatine the University of Guelph, told CBS News successful an email. 

Gregory coined this nickname in March, and it gained traction among the variant trackers who person spotted and nicknamed galore distinctive changes to the microorganism during the pandemic. Though unofficial, these nicknames person go commonly utilized names for a fig of variants.

FLiRT won retired implicit different nickname — "tiLT" variants — which had been coined by Australian advisor Mike Honey. FLiRT refers to a postulation of faster-growing JN.1 offshoots the trackers are keeping an oculus on, KP.2 among them.

"Basically, beauteous overmuch everything close present is simply a descendant of BA.2.86.1.1 (JN.1) and things are evolving rapidly, truthful it makes much consciousness to absorption connected mutations of involvement alternatively than idiosyncratic variants for the clip being," wrote Gregory.

Do FLiRT variants pb to antithetic COVID-19 symptoms?

Unlike immoderate erstwhile highly mutated variants that had raised concerns implicit imaginable changes to symptoms successful caller years, the JN.1 variant galore Americans already apt caught implicit the wintertime is intimately related to the KP.2 strain present connected the rise. 

"Based connected existent information determination are nary indicators that KP.2 would origin much terrible unwellness than different strains," a CDC spokesperson told CBS News. 

KP.2's 2 distinctive alleged FLiRT mutations person besides been seen before, successful XBB.1.5 variants that were circulating passim 2023, the spokesperson said. 

A draught study from scientists successful Japan, released arsenic a preprint that has yet to beryllium peer-reviewed, recovered that the variant did look to dodge antibodies amended than the JN.1 variant. This "increased immune resistance" apt explains its rise, the scientists said.

In general, wellness authorities and experts person downplayed claims that variants were causing antithetic symptoms. Changes to a person's immunity from vaccines and anterior infections often play a relation successful antithetic symptoms, alternatively than circumstantial mutations.

"Mutations hap frequently, but lone sometimes alteration the characteristics of the virus," the CDC says.

Will vaccines enactment against FLiRT variants?

The CDC has not made immoderate changes to its existent vaccine recommendations, which were last updated successful April. But the emergence of these caller JN.1 variant descendants similar KP.2 mightiness impact what vaccine the FDA picks retired for this coming autumn and winter.

Most Americans stay eligible to get astatine slightest 1 dose of this past season's updated COVID-19 vaccine, which CDC data truthful far suggests was up to 51% effectual against exigency country oregon urgent attraction visits during a clip erstwhile JN.1 was connected the rise.

"CDC volition proceed to show assemblage transmission of the microorganism and however vaccines execute against this strain," the bureau said of KP.2.

Last month, the World Health Organization's experts recommended that vaccine manufacturers nutrient shots targeted astatine the JN.1 variant for adjacent season. A sheet of the FDA's ain vaccine experts were scheduled to measurement that attack for the American vaccine marketplace adjacent week. 

However, the bureau recently announced it had decided to hold the gathering until June successful hopes of buying much clip to guarantee it picks retired a vaccine people that is "most due to beryllium utilized for the strain(s) anticipated to beryllium circulating" successful the fall.

"The FDA, on with its nationalist wellness partners, cautiously monitors trends successful the circulating strains of SARS-CoV-2. As has happened since the emergence of COVID-19, we person precocious observed shifts successful the ascendant circulating strains of SARS-CoV-2," an FDA spokesperson told CBS News successful a statement.

Pfizer has generated information from probe of its vaccines against KP.2, but a institution spokesperson said they were presently incapable to stock the results. A Moderna spokesperson did not respond to a petition for comment.

A Novavax spokesperson said they had information showing their vaccine campaigner for the autumn aimed astatine JN.1 has "good cross-reactivity" for KP.2. While Novavax's vaccine takes longer to marque than the mRNA shots from Pfizer and Moderna, the spokesperson said FDA's hold to the gathering "will not affect" their quality to present a changeable this fall.

"We person manufactured JN.1 accordant with the recommendations and are connected way to present an updated vaccine this fall," the Novavax spokesperson said.

Alexander Tin

Alexander Tin is simply a integer newsman for CBS News based successful the Washington, D.C. bureau. He covers the Biden administration's nationalist wellness agencies, including the national effect to infectious illness outbreaks similar COVID-19.

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